a, abbr, acronym, address, applet, article, aside, audio, b, big, blockquote, body, canvas, caption, center, cite, code, dd, del, details, dfn, div, dl, dt, em, embed, fieldset, figcaption, figure, footer, form, h1, h2, h3, h4, h5, h6, header, hgroup, html, i, iframe, img, ins, kbd, label, legend, li, mark, menu, nav, object, ol, output, p, pre, q, ruby, s, samp, section, small, span, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, time, tr, tt, u, ul, var, video {
    margin: 0;
    padding: 0;
    border: 0;
    font-size: 100%;
    font: inherit;
    vertical-align: baseline;
}

article, aside, details, figcaption, figure, footer, header, hgroup, menu, nav, section {
    display: block;
}

div {
    display: block;
}

img {
    width: 100%;
    vertical-align: top;
}
a {
    display: block;
    text-decoration: none;
}


ul,ol{
    list-style: none;
    padding: 0px;
    margin: 0px;
}

.fn_viewport {
    width: 20rem;
    margin: 0 auto;
}

/*只有知道所有的屏幕尺寸时这种方式适用*/

@media only screen and (width: 320px) {
    html {
        font-size: 16px;
    }
}
@media only screen and (width: 360px) {
    html {
        font-size: 18px;
    }
}
@media only screen and (width: 375px) {
    html {
        font-size: 18.75px;
    }
}
@media only screen and (width: 393px) {
    html {
        font-size: 19.65px;
    }
}
@media only screen and (width: 400px) {
    html {
        font-size: 20px;
    }
}
@media only screen and (width: 414px) {
    html {
        font-size: 20.7px;
    }
}
@media only screen and (width: 640px) {
    html {
        font-size: 32px;
    }
}
@media only screen and (min-width: 640px) {
    html {
        font-size: 32px;
    }
}